Influence of laser coagulation therapy on untreated fellow-eyes in severe nonproliferative diabetic retinopathy-spectrometric results

PURPOSE

The aim was to examine the influence of laser treatment on untreated fellow-eyes.

METHODS

The effectiveness of the laser photocoagulation was investigated in 24 patients with type II diabetes mellitus and severe nonproliferative diabetic retinopathy. Using a spectrometric technique, the measurements in the macula were performed one day before laser coagulation and on the day directly following laser treatment. Further investigations took place 14 days and 6 weeks later.

RESULTS

One day after coagulation, the reflection of the untreated fellow-eyes was found to be significantly increased between 530 and 600 nm, compared to the same eyes before coagulation. However, 14 days and 6 weeks after laser treatment alterations in the untreated eyes were no longer detectable.

CONCLUSION

The choroidal blood volume seems to be decreased not only in coagulated eyes, but also in untreated fellow-eyes, and, presumedly, the choroidal blood flow is improved. Considering the short duration of these effects, a therapeutic consequence is not supposed.

[Online measurement of retinal artery branches in type II diabetic patients. Initial clinical trials before and after laser coagulation]

By the use of a new online measuring system the effect of argon-laser coagulation in diabetics on the diameters of retinal arteries was measured.

METHOD

The vessel diameter of retinal branch arteries were measured in patients with type-II diabetes before and after (0.5 h) argon-laser coagulation. Ten patients without previous laser treatment were included in this study. Measurements were taken in all four quadrants by the use of a new automatic online measuring system.

RESULTS

The new technique allowed measurements to be made within an acceptable period of time and with little strain on patients. After argon-laser coagulation 56.7% of retinal arteries showed a significant vasodilation. No significant changes in vessel diameter were found in 18.9% of these arteries, whereas 24.3% showed significant vasoconstriction.

CONCLUSION

The new online measuring system is able to measure the effects of photocoagulation on an individual basis with a noninvasive technique. The first findings presented here confirm previous studies of larger groups, with a considerable reduction in efforts required.

Vitreous levels of vascular endothelial growth factor are not influenced by its serum concentrations in diabetic retinopathy

Vascular endothelial growth factor (VEGF) plays a major role in the development of neovascularization in proliferative diabetic retinopathy (PDR). The source of intravitreous VEGF is presumably ischaemic retina, but increased levels derived from serum cannot be excluded. The aim of the study is to determine the intravitreous concentrations of VEGF in diabetic patients with PDR and to investigate whether serum VEGF could contribute to the intravitreous concentration. For this purpose, we studied 20 diabetic patients (5 IDDM and 15 NIDDM) with PDR in whom a vitrectomy was performed (group A). Non-diabetic patients (n = 13) with other conditions requiring vitrectomy served as a control group (group B). In both groups, VEGF was determined in serum and undiluted vitreous samples obtained simultaneously. Furthermore, serum VEGF was determined in 69 healthy control subjects (group C) and 39 diabetic patients without microvascular complications (group D). Vitreous and serum VEGF was determined by ELISA (R & D Systems, Abingdon, UK); intra-assay CV 3.8%, interassay CV 5.1%. Intravitreous concentrations of VEGF were strikingly higher in group A (median 1.75 ng/ ml, range 0.33-6.66) in comparison with group B (median 0.009 ng/ml, range 0.009-0.038); p < 0.0001. This difference remained significant after adjusting for intravitreous protein concentration (p < 0.05). Differences in serum VEGF among the groups included in the study were not found. We conclude that the high vitreous levels of VEGF observed in diabetic patients with PDR cannot be attributed to serum diffusion across the blood-retinal barrier. Therefore, intraocular synthesis is the main contributing factor for the high vitreous VEGF concentrations observed in PDR.

Elevated gamma-aminobutyric acid, glutamate, and vascular endothelial growth factor levels in the vitreous of patients with proliferative diabetic retinopathy

OBJECTIVE

To examine the relative levels of gamma-aminobutyric acid (GABA), glutamate, and vascular endothelial growth factor (VEGF) in the vitreous of nondiabetic and diabetic patients.

METHODS

Undiluted vitreous samples were obtained from 22 patients with proliferative diabetic retinopathy (PDR) and 28 patients without diabetes who underwent pars plana vitrectomy. Simultaneous venous blood samples also were obtained. Amino acid concentrations were determined using sensitive high-performance liquid chromatography, and VEGF levels by quantitative enzyme-linked immunosorbent assay. Hemoglobin concentrations in the blood and vitreous were determined using spectrophotometry.

RESULTS

The level of GABA in the vitreous of patients with PDR, 29.4 +/- 7.8 mumol/L, was significantly higher than in controls (18.4 +/- 5.5 mumol/L) (P = .004). The vitreous concentration of glutamate was higher in patients with PDR (24.7 +/- 14.0 mumol/L) compared with controls (9.1 +/- 5.1 mumol/L) (P < .001). Vitreous VEGF level was significantly higher in patients with PDR (1759 +/- 1721 pg/mL) compared with controls (27 +/- 65 pg/mL) (P < .001). There were moderately strong correlations between GABA and VEGF levels (r = 0.68) and glutamate and VEGF levels (r = 0.43). Elevated GABA, glutamate, and VEGF levels also correlated strongly with the presence of PDR. Correcting for possible introduction of these molecules by vitreous hemorrhage did not significantly alter these findings.

CONCLUSIONS

Levels of glutamate potentially toxic to retinal ganglion cells are found in the vitreous of patients with PDR. Elevated vitreous GABA may reflect amacrine cell dysfunction and underlie electroretinographic oscillatory potential abnormalities seen in diabetic retinopathy. The correlations of glutamate and GABA levels with an elevated VEGF level provide biochemical support for ischemia-induced neovascularization in patients with PDR. These findings present opportunities for novel therapeutic modalities in the treatment of PDR.

[Peripheral retinal cryocoagulation. Long-term outcome]

Peripheral retinal cryotherapy alone, without additional cyclocryotherapy, can for the short term lead to intraocular pressure reduction and regression of neovascularization. As there is little information concerning the long-term results of this treatment we reexamined all patients treated with peripheral retinal cryotherapy at the Department of Ophthalmology at Freiburg University between 1979 and 1990.

PATIENTS AND METHODS

Neovascularization was secondary to proliferative diabetic retinopathy in 33 eyes (65%), secondary to retinal vascular occlusion in 13 eyes (25%), and secondary to a combination of both in 5 eyes (10%). Usually, 2 quadrants of each eye were treated with 9 applications per quadrant.

RESULTS

Intraocular pressure was adequately reduced in 49% of the eyes and rubeosis iridis regressed in 57%. Visual acuity deteriorated in 53% of all cases.

CONCLUSION

Intraocular pressure and rubeosis iridis can in the long term successfully be treated with peripheral retinal cryotherapy. Despite good intraocular pressure control and regression of rubeosis iridis visual acuity does not improve.

Vitrectomy for traction macular detachment in diabetic retinopathy

BACKGROUND

A small number of eyes with proliferative diabetic retinopathy develop massive central fibrovascular membranes characterized by vitreoretinal tractions along the arcades and optic disk and retinal traction lines extending through the macula. The aim of our study was first to present the results of vitrectomy for removal of these central membranes and second to determine the correlation between preoperative parameters and postoperative visual outcome.

SUBJECTS AND METHODS

We treated 28 eyes with severe central fibrovascular diabetic membranes by a modified bi-manual en bloc excision technique during vitrectomy. Preoperative examination included general status, visual acuity, slit-lamp investigation, binocular funduscopy, ultrasound investigation and visual evoked potentials (VEP). Further, we analyzed intraoperative complications and postoperative anatomic and functional outcomes.

RESULTS

The retinas of 27 eyes with central traction retinal detachments were reattached by surgery. With a minimum of 6 months' follow-up, the macula remained attached in 24 eyes, while the retinas were completely attached in 22 eyes. Preoperative visual acuity was defective light perception to 0.1; an increase in visual acuity to maximal 0.1 was seen in 50% of the patients postoperatively. Preoperative visual acuity of light perception was associated with no functional improvement. Preoperative ultrasound investigation gave information about the real anatomic situation of the retina, especially if funduscopy was not possible. The other preoperative parameters could not predict correctly the functional outcome of vitrectomy in diabetics with severe central fibrovascular membranes because of the damage of the optic nerve and the retina.

CONCLUSIONS

The high rate of anatomical reattachment after vitrectomy in diabetic eyes with severe central fibrovascular membranes is associated with a slight improvement of function; only preoperative visual acuity of hand motions or better was associated with an improvement of function.

Diode laser (810 nm) versus argon green (514 nm) modified grid photocoagulation for diffuse diabetic macular edema

OBJECTIVE

To compare argon green (514 nm) versus diode laser (810 nm) modified grid laser photocoagulation treatment in diffuse diabetic macular edema (DDME).

DESIGN

Randomized, prospective clinical trial.

PARTICIPANTS

Patients with DDME and diabetic retinopathy of fewer than two high-risk characteristics in severity, no previous laser photocoagulation for diabetic macular edema, and no other ocular condition that could interfere with assessment of treatment results.

INTERVENTION

One hundred seventy-one eyes of 91 patients were randomized to either argon green (514 nm) or diode laser (810 nm) modified grid laser photocoagulation for DDME. Follow-up was conducted for a minimum of 12 months (16.55 +/- 3.52 months). Retreatment was performed for residual edema involving the foveal avascular zone.

MAIN OUTCOME RESULTS

Visual improvement, visual loss, reduction-elimination of macular edema, and the number of supplemental treatments.

RESULTS

A comparison of visual improvement, visual loss, reduction-elimination of macular edema, and the number of supplemental treatments showed no statistical difference between the groups (P > 0.05 for all groups). Reduction-elimination of DDME was better in the group without cystoid macular edema than the group with cystoid macular edema, but visual outcome appeared to be similar in both groups. History of hypertension or poor initial visual acuity (< or = 20/80) at entry into the study had no significant effect on the outcome. However, the patients without systemic vascular disease have improved more than those with systemic vascular disease regardless of the type of the laser used.

CONCLUSIONS

Diode laser (810 nm) modified grid laser photocoagulation for DDME is equivalent to argon green (514 nm) and patients without systemic vascular disease are more likely to improve after laser treatment with either wavelength.

Photographic detection of retinopathy in insulin-treated diabetes. A population study in the city of Tartu, Estonia

PURPOSE

To perform a cross-sectional baseline investigation of diabetic retinopathy prevalence and metabolic control.

METHODS

Using a register of insulin-dependent diabetes mellitus in Tartu (pop. 104,791), 175 patients were invited to fundus photography; 149 (89%) participated, 99 of them diagnosed with diabetes before the age of thirty. Four Kodachrome 64 photographs per eye were taken with a Canon CR4 - 45NM camera through tropicamide-dilated pupils; slides were projected and systematically graded. Capillary blood samples (n = 132) for HbA1c determination were mailed on filter paper. Following cysteine buffer elution, Mono S ion exchange chromatography was performed (reference range 3.7 to 5.3%).

RESULTS

Any diabetic retinopathy was found in 114 patients (76.5%; 95% confidence interval, CI, 70 to 83%); mild to moderate non-proliferative retinopathy in 59 (40%; 95% CI 32 to 48%); severe non-proliferative retinopathy in 29 (19.5%; 95% CI 13 to 26%); proliferative retinopathy in 26 (17%; 95% CI 11 to 24%); 47 patients (32%) needed laser photocoagulation. Vitreous haemorrhage was observed in 9 (6%) of subjects. In patients diagnosed with diabetes before the age of 30 years, prevalence of any retinopathy was 82% (95% CI 73 to 89%) and of proliferative retinopathy 23% (95% CI 15 to 33%). Median HbA1c was 9.7% for women and 8.6% for men (95% CI for difference 0.7 to 2.1%).

CONCLUSION

Retinopathy prevalences (76-82%) are the highest reported from population-based studies. Glycaemia levels were very high and should be gradually lowered. Methods capable of validation can be successfully introduced for population-based assessment of hyperglycaemia and retinopathy prevalences.

Fluorometric evaluation of panretinal photocoagulation in diabetic subjects

The effect of panretinal photocoagulation on the blood-retinal barrier was examined by long-term kinetic vitreous fluorophotometry in eight insulin treated diabetic subjects, before and one month after unilateral panretinal photocoagulation. The fluorophotometric investigations revealed an increased permeability-index following this treatment. A further analysis based upon a two-compartment fluorescein kinetic model revealed a decreased penetration rate constant together with increased zero-time concentration coefficients for fluorescein following panretinal photocoagulation. No alterations were observed in kinetic parameters in the group of untreated eyes. This points towards a delayed but increased fluorescein penetration to the vitreous following panretinal photocoagulation, probably indicating an increased net flux of fluorescein across the entire retina. In patients with unilateral proliferative retinopathy the permeability-index obtained from eyes with classified proliferative retinopathy was 18.1%, whereas the permeability-index from eyes without proliferative retinopathy was 15.4%. This relatively small difference seems to indicate that the main part of vitreous fluorescence comes from an increased penetration across the entire retina, whereas a direct leakage from the proliferations themselves is less in magnitude. This increased retinal penetration might possibly be caused by affected transport processes for fluorescein within the retina.

Vitreoretinal surgery assisted by the 193-nm excimer laser

PURPOSE

Ablating and cutting vitreoretinal membranes using a 193-nm excimer laser-based microsurgical system.

METHODS

A 193-nm microsurgical system enables delivery of the beam into a fluid medium to cut preretinal and subretinal membranes. Two patients with proliferative diabetic retinopathy and one patient with proliferative vitreoretinopathy were treated with this new device.

RESULTS

Gentle ablation and cutting of the preretinal and subretinal membranes without exerting any traction on or apparent damage to the neighboring tissue was achieved.

CONCLUSIONS

The technology is applicable to a variety of intraocular vitreoretinal surgical procedures.

Ciliary body and choroidal detachment after laser photocoagulation for diabetic retinopathy. A high-frequency ultrasound study

OBJECTIVE

The purpose of the study is to clarify the manifestation of the ciliary body after retinal photocoagulation for diabetic retinopathy.

DESIGN

Ultrasound biomicroscopy (UBM) was applied to obtain the tomographic features of the anterior ocular segment.

PARTICIPANTS

Twenty-one eyes of 17 consecutive patients with diabetic retinopathy were included in this study.

INTERVENTION

These eyes were treated by panretinal photocoagulation divided in four sessions. In the first session, the nasal quadrant of the fundus was treated with argon or dye (590 nm) laser totaling 208 to 331 spots per eye.

MAIN OUTCOME MEASURES

The eyes were examined by UBM before, immediately after, 3, and 7 days after the first session of photocoagulation.

RESULTS

Three days after photocoagulation, ciliochoroidal detachment was observed in 19 eyes (90%). The detachment was present along the whole circumference. The ciliary detachment was most prominent in the pars plana in 19 eyes and extended to the pars plicata in 9 eyes. It spontaneously had disappeared 7 days after photocoagulation.

CONCLUSIONS

Ciliochoroidal detachment was a very frequent feature after sector photocoagulation in diabetic eyes. Although this complication was asymptomatic and transient so far, this potential hazard merits due attention in the planning of panretinal photocoagulation in diabetic eyes.

Phacoemulsification for cataract following pars plana vitrectomy

BACKGROUND AND OBJECTIVE

To determine if the technical aspects of phacoemulsification for removal of cataract following pars plana vitrectomy differ from those of phacoemulsification for removal of cataract in nonvitrectomized eyes.

PATIENTS AND METHODS

Twenty-two eyes that had undergone prior vitrectomy were identified through a retrospective review of chart notes and operative records of 1039 consecutive cataract extractions performed by one surgeon.

RESULTS

Complications of proliferative diabetic retinopathy was the most common indication for prior vitrectomy. The predominant lens change was nuclear sclerosis. Deep anterior chambers with large anterior to posterior excursions of the iris lens diaphragm with simultaneous fluctuation in pupil size occurred during phacoemulsification. The posterior capsule was flaccid and mobile during lens cortex removal. No posterior capsules ruptured. Postoperative visual acuity improved in 91% of the patients.

CONCLUSIONS

Prior vitrectomy was associated with diabetes and nuclear sclerotic cataract. Phacoemulsification in this patient population was associated with inadequate pupillary mydriasis, superior conjunctival scarring, intraoperative anterior chamber depth, pupil size, and iris lens excursions that hindered phacoemulsification tip placement. Posterior capsules were excessively flaccid, prone to rapid anterior and posterior excursions, and may have plaques that are resistant to intraoperative removal.

[Changes in the electroretinogram of eyes with diabetic retinopathy treated by vitrectomy]

Flash electroretinogram (ERG) and 30 Hz flicker ERG before and after operation were tested in 55 eyes of 46 patients with proliferative diabetic retinopathy who were treated by vitrectomy. The results were evaluated with preoperative ocular findings -the existence of retinal detachment, posterior vitreous detachment, panretinal photocoagulation (PRP) and vitreal hemorrhage and intraocular tamponade materials. In the group without retinal detachment, the amplitude of the ERG b-wave and a-wave after vitrectomy decreased significantly if PRP was not done before operation. In the group with retinal detachment, when retinal detachment was restricted to the posterior pole of the fundus, when posterior vitreous detachment had occurred in only a small area of the fundus, when there was vitreous hemorrhage or when silicone oil was injected in the operation, the amplitude of the ERG b-wave and a-wave decreased significantly after the operation. In both groups, the latency of 30 Hz flicker ERG was shortened significantly after vitrectomy.

Influence of panretinal photocoagulation on the ocular pulse curve

PURPOSE

To study the ocular pulsation amplitude (an indicator of choroidal circulation) and systolic ophthalmic artery pressure after panretinal photocoagulation.

METHODS

Prospectively, in 10 patients with diabetes mellitus (eight with type II and two with type I; mean age, 64 years) and severe, hitherto untreated, bilateral proliferative diabetic retinopathy, we performed intensive, unilateral panretinal photocoagulation with 1,500 argon laser burns (spot size, 500 microm) in two sessions (interval, 3 weeks). Before and (in 3-week intervals) up to 9 weeks after treatment, we recorded ocular pulse curves using oculo-oscillodynamography and determined each patient's ocular pulsation amplitude and systolic ophthalmic artery pressure.

RESULTS

Compared with the untreated contra-lateral eyes, panretinal photocoagulation led to a reduction of ocular pulsation amplitude. Three weeks after the first coagulation, the reduction averaged 20%. Maximum reduction was found 9 weeks after onset of treatment (6 weeks after the second coagulation) and amounted to 29.9%. The differences between photocoagulated and untreated eyes were highly significant on average (P < .01; analysis of variance) as well as for time course (P < .001). Systolic ophthalmic artery pressure was not changed significantly during panretinal photocoagulation follow-up.

CONCLUSIONS

Ocular pulsation amplitude is determined by the cardiac cycle-related intraocular volume changes that depend predominantly on choroidal blood flow. The morphologic substrate is probably choriocapillary closure after photocoagulation.

Secondary vitrectomy for the treatment of macular holes occurring after vitrectomy

Tangential foveal traction by the posterior vitreous cortex is regarded as the main cause of full-thickness macular holes. This report documents two cases of full-thickness macular holes that developed after vitrectomy for other diseases in the apparent absence of the cortical vitreous traction. Autologous serum with pars plana vitrectomy was used to treat these cases. Anatomic closure of the holes was achieved. Macular holes developing after vitrectomy may have an etiology other than tangential vitreous traction, and secondary vitrectomy is useful in treating such holes.

[Long-term vision follow-up after vitrectomy in diabetic retinopathy]

BACKGROUND

We investigated whether visual acuity remained stable in the long run after vitrectomy for complications of diabetic retinopathy and which risk factors for a decrease in vision could be identified.

MATERIALS AND METHODS

The charts of 389 patients who had undergone vitreous surgery for complications of diabetic retinopathy between 1990 and 1994 were retrospectively reviewed. The median follow-up was 26 months with a minimum of 6 months.

RESULTS

Seventy-two percent of the eyes with a vision of 20/200 or better within 6 months after surgery retained this vision after 2 years. The percentage of eyes with vision of less than 5/200 was 25% after 6 months and increased to 41% after 4 years. After 2 years 24% of the eyes had lost two or more lines compared to the best vision within the first 6 months after surgery. The main cause for a decrease of vision in type-I diabetics was retinal detachment, in type-II diabetics a progression of maculopathy and opticopathy. Risk factors for a detachment were pre-existing retinal detachment before surgery and reduced postoperative vision. The risk factor for a progression of maculopathy and opticopathy was a silicone tamponade.

CONCLUSIONS

Eyes with good vision soon after surgery remain stable in the long run. Eyes with advanced stages of diabetic retinopathy and only ambulatory vision after surgery have an increased risk for new loss of visual function in the long run.

The effect of patient characteristics on response to focal laser treatment for diabetic macular edema

PURPOSE

The purpose of the study was to determine which patient characteristics influence response to focal photocoagulation for clinically significant diabetic macular edema (CSME).

METHODS

A retrospective chart review was performed of 547 eyes from 361 patients who were observed for at least 1 year (mean, 2.6 +/- standard deviation 1.7 years) after surgery. Preoperative patient characteristics were tested for their significance in predicting outcome using multiple regression analysis.

RESULTS

Increasing patient age has a negative effect on visual outcome (P = 0.0179). Patients with diet-controlled diabetes show improvement in mean vision, whereas patients whose diabetes is controlled with insulin, oral agents, or both show declines, and these differences are significant (P < 0.0001). Neither cataract surgery before or after focal photocoagulation nor simultaneous panretinal photocoagulation for patients having concomitant high-risk proliferative retinopathy had a significant effect on outcome.

CONCLUSIONS

Younger patients with CSME and those with diet-controlled diabetes can be given more favorable prognoses. Patients with CSME and high-risk proliferative disease can have cost-effective simultaneous focal and panretinal photocoagulation without adversely affecting visual outcome.

Fluorescein angiography of peripheral retina and pars plana during vitrectomy for proliferative diabetic retinopathy

PURPOSE

To evaluate the extreme peripheral retina and pars plana during vitrectomy in patients with proliferative diabetic retinopathy.

METHODS

In a prospective study using a modified ophthalmic endoscopic system and an intraocular light source, we performed fluorescein angiography during pars plana vitrectomy in 12 eyes of 10 patients with proliferative diabetic retinopathy. Vitrectomy had been performed previously in two patients, and the subsequent surgery was necessary because of recurrent vitreous hemorrhage in one patient and silicone oil removal in the other.

RESULTS

All 12 eyes of 10 patients demonstrated a wide avascular area in the peripheral retina anterior to the previous photocoagulation scar. At the ora serrata in two eyes, a fibrovascular ridge of peripheral retinal vessels with fluorescein leakage that resembled the demarcation line in retinopathy of prematurity was noted; one eye had developed neovascular glaucoma 4 weeks after vitrectomy with maximum augmentation of endolaser photocoagulation, and the other eye had neovascular glaucoma that had been treated with photocoagulation 1 year before vitrectomy. In the two eyes that had undergone previous pars plana vitrectomy, fluorescein leakage was apparent at the fibrous scar of the sclerotomy site.

CONCLUSION

Intraoperative fluorescein angiography using an endoscope disclosed unusual findings in the extreme peripheral retina and pars plana of patients with proliferative diabetic retinopathy. Intraoperative fluorescein angiography may aid intraoperative evaluation and treatment of proliferative diabetic retinopathy.

[Cryocoagulation in therapy of proliferative diabetic retinopathy]

BACKGROUND

The importance and indication of panretinal photocoagulation in proliferative diabetic retinopathy is well established. In contrast the indication of cryotherapy in this disease is more controversial especially in regard of new indications for early vitrectomy. The present study was performed to characterize the clinical possibilities and limitations of cryotherapy in complicated proliferative diabetic retinopathy.

PATIENTS AND METHODS

In 231 patients with proliferative diabetic retinopathy and vitreous hemorrhage limiting further photocoagulation the visual outcome and diabetic retinal changes were observed before and after cyrotherapy (15-20 effects) of the ophthalmoscopically visible peripheral retina.

RESULTS

After cryotherapy regression of active proliferations could be seen in 70% of the patients. Resorption of vitreous hemorrhages could be found in 80% of the patients. This was associated with improvement in visual acuity in 50-60% of the patients. Loss of vision was caused due to tractional detachment in 20% of the patients and due to further vitreous hemorrhages in 10% of the patients. Comparison of retinal changes between patients with worsened visual acuity and patients with increase in visual acuity demonstrated the preoperative fibrotic status of disc neovascularisation as the most important prognostic factor. The development of central tractional detachment was significantly higher in patients with preoperatively partly regressed disc neovascularisation.

CONCLUSIONS

Cryotherapy of the peripheral retina in proliferative diabetic retinopathy with vitreous hemorrhages is therefore only indicated after ophthalmoscopical or echographical exclusion of peripapillary fibrosis and retinal traction and with sufficient visibility of the peripheral retina for the application.

The pattern electroretinogram (PERG) after laser treatment of the peripheral or central retina

PURPOSE

To understand whether laser photocoagulation of the retina for the treatment of diabetic retinopathy (DR) alters directly or indirectly the function of the macular region.

METHODS

Transient pattern electroretinograms (PERGs) to 30' checks have been recorded in DR patients before and 7-10 days after one treatment session (established protocol with Argon laser) of either the peripheral retina (panretinal treatment) or the central retina (paramacular focal treatment).

RESULTS

Treatment of the peripheral retina causes, in most eyes, a small increase (about 15% on average) of the PERG amplitude. Focal paramacular treatment causes a marked decrement (about 40% on average) of the PERG amplitude. Simulated retinal amputation induced by focal treatment, obtained by means of adequate stimulus masking, resulted in a 15-20% PERG decrement only.

CONCLUSIONS

The PERG increase after peripheral treatment may be due to rearrangement of both retinal and choroideal hemodynamics and does not necessarily result in useful long term changes. The PERG decrease after focal, paramacular treatment is far larger than that expected on the basis of the amputated area only. This may result from thermal and/or toxic damaging effects spreading outside the treated area. The results are relevant for both a better monitoring of central retinal function in the course of laser treatment and a better evaluation of the cost/benefit ratio after photocoagulation in DR.